NVIDIA also shared some performance details and it seems the card will indeed barely be faster than the RTX 3080. Despite costing over double as much, the RTX 3090 will offer just 10-15 percent higher 4K gaming performance than the RTX 3080:
For gamers pushing the limits, the GeForce RTX 3090 is also the first GPU that lets you connect, play, capture, and watch in 8K HDR. That’s an insane 4x the pixels of 4K and 16x the pixels of 1080p.
For 4K gaming, the GeForce RTX 3090 is about 10-15% faster on average than the GeForce RTX 3080, and up to 50% faster than the TITAN RTX.